Chapter 1: My obsession with asphalt was born on a bike ride through a cemetery

I don't remember how I ended up there that day. Maybe I pedaled up for the view, a smashing panorama of the San Francisco skyline that lies at the end of a grand network of roads and paved lanes that reach up into the hills. Or maybe I was delaying the end of a too-short ride by tacking on a detour that meandered among prim headstones and Munsteresque family crypts. What I do remember clearly is sensory—sniffing the freshly cut grass near the entrance, then noticing the sound of my tires on the pavement, something like sizzling bacon. As I started riding uphill, the smooth, black, buttery layer of asphalt gave way to something crunchy, like the crumb topping on a coffee cake. Little cascades of stones skittered away from my tires. The pavement changed again, tight and brownish. Cracks appeared, then a puzzling, fresh patch of pitch-black asphalt. There came a pothole. And, just past a grave labeled Nutter, the pavement gave up entirely, and the road turned to dirt.

All the major existential questions rushed at me: Why does some asphalt stay and some asphalt go? Where do roads come from? What was that sizzling sound? When I was four, a paving crew appeared one summer day in front of our house. My mom, who enjoyed fermenting sauerkraut at home, warned me to stay far away from the commotion. I spent the day watching the birth of a road from behind a shrub. Asphalt was black and shiny, steaming hot, apparently somewhat gooey, and it reeked of decayed dinosaur. Irresistible. No sooner had the crew departed for the day than I took off my shoes and ran toward the road, hoping to leave an impression of my feet. I jumped onto the blacktop—and had a Wile E. Coyote moment, becoming a cartoon child frozen in midair, puffs of black smoke tooting from my feet, eyes like fried eggs, legs pleated like accordions, etc.

Back at the curb, I was disappointed to see that I'd left no impression on the blacktop whatsoever. Worse, the new road had left its mark on me—clots of gunky black tar clung to the ball of each toe. The clots would not come off. I was marked. Ten toes carried the black spot—proof that I'd not only "gone near the asphalt," but also committed the spanking-worthy crime of "playing in the road." My heart pounded. Punishment was nigh. Then a deception occurred to me: socks. I put on socks and kept them on for days.

And so, asphalt became my first furtive pleasure.

Under the cumulative strain of later furtive pleasures—none appropriate for a cycling magazine—asphalt had faded from my consciousness. Like anyone who rides a bicycle, I was aware of its effect on me from time to time. But there in the cemetery, it struck me that despite all the effort cyclists put into understanding how to ride—how to train and handle a bike, eat properly and perform maintenance—and despite the appreciation we lavish on smooth roads and the disdain we heap upon broken pavement, we know almost nothing about the surface on which our wheels spin. Maybe it's just as well, because once I started really thinking about the literal foundation of our sport, it was easier to keep going than to stop.

Chapter 2: Our bikes are designed to isolate us from pavement

We feel the road through vibration-absorbing frames and gel saddles and shock-absorbing seatposts and thick, padded handlebar tape. The only time we really experience asphalt is when our tires stop grabbing it, and we fall.

That moment seemed as good a place as any to begin. It turned out that the man who understood why bike tires fall prey to what people who study such things call slip out was Jobst Brandt, an engineer and author of The Bicycle Wheel, the seminal work on the subject. Brandt informed me that the interaction of tire and pavement fell under the subject of tribology—the study of friction, lubrication and wear.

In the 1980s, he said, he wanted to analyze how tires perform on real pavement—at what angle do they slip out? How do they behave differently on wet roads? To do this, he had to create a machine that allowed the asphalt to move and the bike to stand still. He built a wheel 6 feet in diameter and 2 feet wide, and paved it "like a typical freeway ramp," he says. Then he rigged up a fork that would hold a bicycle wheel against the asphalt with the same pressure a human rider would exert. When he cranked the thing up he could precisely measure the slip-out angle of different tires. He could even simulate rain with a squirt bottle attached above the asphalt wheel. The contraption sounded like a cross between a human-size hamster wheel and one of those Tibetan diagrams of the cosmos. Naturally, I wanted to see it. But Brandt said he didn't have it anymore and gave me a phone number to call.

The number was the home phone of Bud Hoffacker, president of Avocet, who expressed no surprise that I was calling about a 20-year-old, 6-foot wheel of asphalt. "Yes," he confirmed, "we spent several hundred thousand dollars on that."

No, I could not see it, because it was in storage. But Hoffacker summarized some of the lessons of the great asphalt wheel: Bumps and ruts in pavement reduce the slip-out angle of any tire by five to eight degrees, making falls more likely. Metal grates reduce the slip-out angle by half.

And, as it turns out, pavement is not a mere surface, a superficial plane we roll across unchanged. The road alters us—or at least our wheels. Michelin tire designer Mark Ludlow explained to me that road textures and temperatures actually change the molecular organization of the rubber in tires.

Like chewing gum, rubber is viscoelastic—yank it on a cold day when it is hard, and it snaps; pull it slowly on a hot day and it stretches, getting softer and gooier. When tires roll over a road, they are heated by friction, and the rubber vibrates in response to the size and shape of the grains of gravel in the pavement. When all goes well, the rubber in the tire is soft enough to grab the road but hard enough to avoid leaving a black mush of itself behind.

But when a tire starts to slide on pavement, something different happens. "Little rocks agitate the tread block and the rubber itself gets stiffer," says Ludlow. "It starts to bounce over the tops of the rocks instead of draping between them and gripping. That's when you hear the tires squealing. There are also things going on that you don't hear. Maybe a dog hears them. I don't know."

Ludlow told me he cannot be on a road without hearing all sorts of clamor—pavement noise, tread noises and that sizzle. "Once you find those sounds," he says, "you hear them always."

Chapter 3: Tires begat roads, not the other way around

When the first modern bicycle, the non-highwheeler safety, arrived on two fat, air-filled rubber tires in the 1880s, tens of thousands of new cyclists hopped on and pedaled furiously into the middle of a social revolution. The popularity of bicycles began changing the country in ways that hadn't been anticipated. Women abandoned skirts for bloomers, hastening the conflicts that fueled the woman's rights movement; preachers complained that their parishioners were deserting the church to ride through the countryside; pump organ sales fell off, according to Dan McNichol, author of The Roads That Built America, suggesting, perhaps, that pump organists were people who liked pumping rather than people who liked organs. Not the least of the social consequences was that all of these bike riders soon found themselves stuck in rutted, muddy lanes that were sometimes derisively referred to as mud canals. The riders began to agitate for smooth, drained, graded roads. The League of American Wheelmen had 80,000 members by 1896, the year its president, Sterling Elliot, said, "You cannot press the crown of muddy roads on the heads of the laboring wheelman: You shall not crucify him upon a crossroads so rough that a duck could not navigate them in gum boots." He was mocking a campaign speech made by William Jennings Bryan, but it was no joke: Cyclists were developing political clout. A year later, 20,000 cyclists elected the mayor of Louisville, Kentucky, according to historian Joe Ward, because he promised to pave Broadway and prevent dust-averse homeowners from sprinkling bike routes with so much water they turned into a "perfect loblolly" of mud.

The demand for rideable roads led to the invention of byways better than cobblestones, which not only clogged with horse manure but also, according to one historical source, caused a "nerve-rasping noise" when horses walked on them. Macadam, made of layers of graded stone, was the road of the moment until the 1900s, when asphalt's rise in popularity really took off. The first successful asphalt in the United States was installed in (where else?) New Jersey in 1870. In 1896, New York City switched from brick and granite to asphalt for new paving, and by the mid 1930s, asphalt was used in more than 4/5 of all highway paving.

In the early days of asphalt, all the gooey tar came from a big, natural asphalt lake in Trinidad. At the top of an extinct volcano, Pitch Lake is 115 acres of sludgy crude oil, which urps to the surface from a reservoir far below. The lake acts as a giant mixer, whirling very dense crude oil together with water and clay to form a hardy glop. The lake provided almost all of the world's asphalt until 1900, when oil refineries began to make the stuff from waste. Maybe in those days asphalt had a more mystical air: The lake also coughed out giant sloth bones, a mastodon tooth and, in 1928, a 4,000-year-old tree, which jutted 10 feet above the surface for a few days before taking itself back to the depths. Likewise, the construction of asphalt roads was hit or miss, more art than science. Many cracked, degenerated quickly, fell apart.

Farmers weren't crazy about even the best asphalt roads. They called cyclists scorchers and peacocks—snooty city slickers who coveted fancy, fast-speed zones without regard for how much they cost hardworking taxpayers (such as farmers). So the political fight for good roads stretched across decades. The League of American Wheelmen eventually ceased holding rallies and making goofy, roof-raising speeches. Instead they started publishing a wonky magazine called Good Roads and earnestly lobbying farmers, railroads and congress.

History hurtled forward, this time on pneumatic tires, and hardly any enthusiasts sat down to consider where all these roads would lead. "The steed of steel is on its conquering way through the universe," wrote the Louisville Courier of the bicycle in 1897. "Soon we may read of it in a great race cavorting around the rings of Saturn."

Chapter 4: Roads are the pyramids and Parthenon of our civilization

Norm also says, "Do not roll down the window. Ignore the dogs." As we drive toward a row of jagged, mismatched fencing, he adds, helpfully, "Just stare straight ahead." Dog eyes appear and reappear in holes in the fence. Dogs yelp and leap. Norm stops the car and squints down at the road. It is blacktop. Standard issue. Not what they came to a mongrel-filled cul-de-sac in Clarksburg, California, to see.

In the backseat, Lloyd sighs, and says, "They've covered up a lot of beautiful pavement."

Before retiring, the two friends worked a total of 90 years for the California Department of Transportation, building bridges during the highway heyday from the late 1950s through the 1970s. "Or maybe," says Lloyd, "We lived the same year 90 times."

Norm Root has big hands and a round face, while Lloyd Johnson is a narrow, precise rectangle, dressed in roughly nine shades of khaki, starting with desert boots and working upward, that camouflage him in the dry grass of the Sierra foothills. Norm takes the opposite tack, with clothing that shouts out his legitimacy—a Lincoln Highway Association hat, T-shirt, pins and photo ID worn on a string around his neck, complemented by the Lincoln Highway Association logo on the truck doors. He keeps an orange CALTRANS vest, an official ID and a hard hat in his Suburban as well, which he sometimes adorns with magnetic CALTRANS decals. Norm and Lloyd are asphalt hunters.

Somewhere beneath us is part of the original Lincoln Highway, the first transcontinental road, which stretched 3,389 miles from New York City to San Francisco. Norm has brought along a list of state-funded work orders. We are on "Clarksburg. 1917. Twelve-foot concrete road. Prison labor."

Clarksburg, once a small town with a school and several sheep ranches, was skipped around by bigger highways, died and was taken over by whirling dogs flinging spirals of frustrated spit. We are not welcome here. Norm puts the Suburban in reverse.

We drive over new, six-lane roads to get to another part of the Lincoln Highway. This section is original: A narrow, white line of concrete with crumbling shoulders rambles delicately around the contours of a hill. These early roads made do with the landscape instead of remaking the land so the roads can be straight. Below us, a new highway cuts across the countryside in a fat line, as though drawn in by a marker. The cars on it sound like a rushing river.

The Lincoln Highway was a sort of publicity stunt for the Panama-Pacific International Exposition. Sniffing opportunity, a bunch of businessmen formed the Lincoln Highway Association to promote the road's use. The promoters included Carl Fisher, who made auto lights; the presidents of Packard and Hudson motorcars; and the head of the Portland Cement Association. "If they could get Americans into cars they'd have some business," explains Norm.

The "highway" was a meandering novelty, a route cobbled together over a patchwork of local roads of widely varying quality. The most primitive sections were dirt. There were sections made of graded stones. There were better roads topped with small stones—aggregate—combined with a binder of either cement or asphalt. Lloyd heads down the slice of Lincoln Highway we're on, pointing out a zebralike patch of cement with big chunks of granite aggregate in it. He tells me that the granite aggregate was made by inmates at Folsom prison working with hammers and chisels. Prison crews made many of California's east-west roads, while the north-south ones were done by contractors. Lloyd walks back, pointing out a seam in the concrete where one day's work stopped and the next began. Norm kicks at the crumbling shoulders on the road, added in 1929, according to the work orders. Here, asphalt was sprayed onto a haphazard mixture of sand, gravel and dirt. Slowly, the asphalt is giving up the stones.

Harvey, a passionate professor of civil and environmental engineering, gets all torn up by damaged pavement. (C.J. Burton)

"If asphalt doesn't get traffic it falls apart," says Norm. "The cars knead the pavement and keep it alive."

The Lincoln Highway's sketchy condition was directly responsible for the creation of the interstate highway system 35 years later. At the end of World War I, the U.S. Army sent a truck convoy—led by a young, bored officer named Dwight D. Eisenhower—across the highway. It took the convoy two months, traveling at an average speed of 6 mph, breaking bridges, getting stuck in the mud and crunching through fragile roads. In 1956, President Eisenhower paved the country with the Interstate Highway Act.

Norm and Lloyd take me to a rough toll road constructed for gold miners in 1852, so steep that travelers had to disassemble their wagons and pull them over the ridge piece by piece. We pay a call to a beautifully graded road built by an engineer named Olgivie in 1861, which still runs nearly intact through the Sierras. Near sunset we drop in on a macadam stretch of the Lincoln Highway, built in 1912 through marshy land and under trees. Twelve feet wide and only a few inches thick, it looks as fragile as a potato chip.

"Imagine," Lloyd says, "Eisenhower rode over this. Right over this. With that military convoy, they could have torn this all up."

The small rocks that make up the surface of the road shine slightly in the low sun. "I highly suspect this was sprayed with asphalt," says Norm, as he checks the work orders for confirmation. "It hasn't been fixed since 1944."

A concrete road, they surmise, would have long ago cracked on this soft marsh ground, while asphalt could drape on the land like a heavy blanket. We are standing in the road like a bunch of Encyclopedia Browns waiting for a eureka moment when Norm, having given up on finding anything useful in the work order, shouts, "Look! You can see the nozzles."

You can, but in reverse. Where the nozzles drizzled asphalt on the road, the surface is ridged, and in places the spray missed, the rocks have all blown away. I have a moment; I feel connected to those men who built our parthenons, long ago.

Chapter 5: Pavement bleeds

"It's bloody highway," snorts J.T. Harvey, professor of pavement in civil and environmental engineering at University of California at Davis. He points at something red, translucent and grisly in the middle of the lane ahead of us, and continues bearing down on it at 60 mph in his pickup truck. Just before we remurder whatever it is, he says, "You think, 'Oh my god, what happened here?' And then you realize, at this time of the year, oh yeah, it's tomato season."

We whisk over the vegetable smear. To Harvey, pavements are so animated they might as well bleed. They are tricky, willful and puzzling, ever-shifting. The only thing a road doesn't do is lie quietly on the ground. "Pavements are really complex structures, more complex than buildings or bridges," he says, "It's harder to build a pavement than to send a man to the moon."

Take the pavement we're on, State Highway 113. Built of more than a foot of concrete, standing on top of aggregate treated with asphalt, which is on top of a tomato field, it gives the impression that it's massive, and passive. To Harvey, though, it's a flat gymnast. During the day it heats up on top and forms a convex curve. At night it cools off and, because the underside is moist, forms a concave curve. Over the years, it will crack under pressure of the double-trailer trucks hauling tomatoes over it. Closer to Davis, the worst has already happened. Moisture has seeped under the joints, washed away the supporting aggregate and left tiles that flap around when we drive over them, making for a bumpy ride and the notorious wuka-wuka sound of flopping concrete. "Rough pavement can increase a truck's fuel consumption by 5 percent," says Harvey, ominously.

Harvey is a big, optimistic man in crisp hiking shorts, but he shoulders what he calls "the curse." Once a relatively carefree music major, Harvey became interested in forestry, then water, and then pavement, which delivered him to his fate. "Before you have the curse, all those cracks in the asphalt are just squiggly lines," he says. "But after you know what caused them, you don't see squiggles, you see deep problems."

At the NCAT, Buzz Powell and his fleet of trucks put pavement through 20 years of wear and tear in two years, and test experimental surfaces designed to achieve such lofty goals as reducing water runoff and muffling. (C.J. Burton)

I'm eager to get the curse. Harvey shuttles me around California so we can stop at various places to experience failed asphalt on bikes. He warns me, "It's like malaria."

First stop: Alligator cracking, named because the grid of cracks makes the pavement look like the back of the giant reptile. Freshly laid asphalt is elastic, but every time a heavy truck drives over it, the pavement bends and returns and becomes weaker. It's like tweaking a coat hanger until it gives way. Depending on the climate, asphalt can withstand hundreds of thousands of heavily weighted axles. Alligator cracks are the mothers of potholes—water seeps into the pavement through the cracks and weakens the pavement until it starts to wash away.

Next: ruts. The tires of heavily loaded trucks and buses push asphalt down and to the sides. If the asphalt is stiff enough, it springs back. But a hot day softens the asphalt, reducing its stiffness and shear strength. A truck that does no damage at eight in the morning may start the first rut in midafternoon, when the pavement is 125 degrees. And it gets more complicated, Harvey explains, because asphalt is viscoelastic (remember the rubber and chewing gum?). The heavier a truck is, the softer the pavement becomes. Even worse, as a truck moves slower, the pavement grows softer and its shear strength lowers. (Pulling chewing gum slowly makes it extra gooey.) So a nightmare, from a pavement engineer's point of view, is a midafternoon traffic jam of trucks in August.

Thermal cracks. Harvey and I are on a Davis, California, bike path. The asphalt appears dark and reasonably fresh, yet it's cut up into large, irregular islands—as though we are riding over a series of isolated asphalt patties. Harvey is baffled. "I'd only expect to see this in Nevada," he says, where extremes of temperature cause asphalt to expand and contract so dramatically it breaks. He muses that perhaps an asphalt mix made for another climate was used here, or that maybe the mix included a stone that's absorbing the binder. Harvey shakes his head and moves on.

For all our pavement, about 2.6-million miles in the U. S. by last count, all we have is practical knowledge—what works and what doesn't. We know very little about the pure science of pavement. Asphalt, for example, is made from asphaltenes, enormous molecules found in crude oil, desirable mainly to road builders and roofers. Asphalt binders are classified by their behavior—how stiff they are, or what temperatures make them soft or brittle.

Harvey tells me he can identify some asphalt binders by smell. But, he adds, almost as an afterthought, "They taste the same."

All in the name of science. Some asphalt researchers forsake eating asphalt and try to further their understanding of how the rocks and a thin layer of binder interact by taking core samples to medical schools at night and running them through the CT scanner to see their 3-D geometry.

Which brings us to the reflection crack. The reflection crack is, to my eyes, a standard, unremarkable scar. To Harvey, though, it is a deep and persistent puzzle. Reflection cracks originate below the surface of the road, in the lower layers. The math problem of reflection cracks, he says, is hard to understand, but necessary to solve. "By the time you're out there filling potholes with a shovel," he says, "you're digging a grave. The patient is already dead."

Chapter 6: Paving is a job for the speedy and precise

Standing among orange cones in the middle of four lanes of rubbernecking traffic, Bill Thomas, wearing a hard hat shaped like a Stetson, looks anxious. Thomas is the head of maintenance for five California freeways in the Bay Area, and he starts every day, and some nights, with a clock ticking in his head: In a single shift he must orchestrate a paving crew to set up the cones, grind out the old pavement, haul it away to be recycled (almost all pavement is recycled—more than 70 million tons a year, more than the combined total of glass, plastic, aluminum and paper, according to the National Asphalt Pavement Association), then have those same trucks pick up the hot mix of asphalt and aggregate at the mixing plant, finally spread and roll the mix before it gets cold, then clean up and get out.

"People are upset when we're out here and people are upset when we're not," Thomas says philosophically. There's never enough time, or money, to fix every road so, he says, they operate under a policy of "worst first."

Today, Thomas is directing the removal of a whole lane of asphalt, 3 inches deep and a few hundred feet long. Some of the nine crew members, dressed in orange jumpsuits, spray asphalt goop in the corners of the lane, while others grind a bump out of the bike lane. Thomas motions a dump truck full of hot mix onto the lane, shutting down traffic in both directions. The truck's dump is coordinated with the motions of a loader, which spreads the steaming-hot mix. It's a smoggy, overcast day and the gooey asphalt folds us into an envelope of petroleum smell, astringent and almost minty. The crew members' movements are so precise and interrelated they appear to be fantastically synchronized, as if they're one of those singing mermaid underwater reviews. But what they're working under is not water but traffic. In the six years between 1992 and 1998, 841 highway workers were killed in the U.S., by construction equipment and passing cars.

When the hot mix is down, the crew works quickly to finish the edges with rakes. This highway lane is getting more hand-finishing than most of the Ikea furniture in my apartment. Finally, the roller runs across the lane, tamping the mix down. I have considered asking to ride on the roller, a lifelong dream, but there is no such luxury. The roller operator is possibly the most important person on the road. Typical asphalt is 6 to 7 percent air. A good roller operator can get that down to 3 percent, which doubles the life of the pavement. A bad roller operator's asphalt will be 12 percent air, and last half as long.

Chapter 7: Pavements are ideas made real

Buzz Powell is blond, with freckles and a conscientious demeanor, and he seems, on the whole, happy to have a visitor. He is the manager of asphalt's tomorrow land, a 1.7-mile loop of pavement in the woods near Opelika, Alabama, operated by the National Center for Asphalt Testing (NCAT), an industry-sponsored organization. Buzz's loop is made of 26 different kinds of pavement, on which a fleet of overloaded semis drives 16 hours a day—to simulate 20 years' highway wear in two years. Each Monday, the trucks rest, and Buzz navigates the track lying on a mechanic's dolly, facedown, to outline every crack in the asphalt with a paint pen, and then videotape it.

By comparing videotapes, he creates crack maps, that show how faults form and travel. "I won't do the cracks this week," Buzz says. "I got real sick out there last Monday."

Today the heat index is supposed to be 116 degrees at noon—already the pine trees surrounding the track are so hot that the facility smells like the candle section at Pottery Barn. Buzz takes me around the track to experience the pavements of the future. We drive across Florida for 200 feet, then onto a project being tested for North Carolina, then Tennessee, Oklahoma and Mississippi. These pavements started as ideas about what would work best in specific situations. Now they are becoming real.

How about a quiet pavement? Here's one with the consistency of caramel corn, creating acoustic chambers to dampen highway sound. "Normally the blocks of tread on a tire act like hammers against the pavement," says Buzz, "and the sound travels around the tire and the tire acts like a speaker." Later in the day a truck equipped with microphones will spin around the track to measure sound levels.

Dry pavement? Buzz points to one with a "stone skeleton," that takes water off the roadway and carries it to the shoulders.

How about a cheap one? Many states have trouble finding inexpensive, high-quality aggregate. (The United States uses 10 tons of aggregate per capita per year. Somewhere there is a mountain of 400 tons of rocks with my name on it.) So pavements test combinations of less-desirable soft aggregates to make cheap but resilient roads. Mississippi, which has no native rock other than sand, silt and gravel, is testing a sand-based road here.

One test pavement was so soft that its aggregate grains became polished and smooth under the truck tires. As an experiment, Buzz applied an epoxy topping made of bauxite to that section; now it resembles sandpaper. Buzz likes that. His ideal road is one on which it's easy to stop.

Besides circling the track on his dolly, Buzz also drives around in a laser-emitting van to measure bumpiness. Then there's the sound-measuring truck. And there are thermometers deep in the pavement, strain gauges, and the other instruments buried in the track. At nearby Auburn University, NCAT has five labs that put slices of asphalt through tortures to induce fatigue, cracking, rutting and general breakdown.

I meet Blake, who runs the truck driving at the track, and who takes me along on the 8 a.m. to 9 a.m. shift. The overloaded truck we ride in, hauling two trailers, spins around the track 25 times that hour. It's August. By mid-December, the five trucks at the track will reach the two-year goal of distributing 10 million axle loads to the pavement. Blake drives along the zipper—the dashed line—a habit left over from the days when he hauled loads, such as Bradley tanks and missile launchers, around the country. Blake says he screens the drivers for this track carefully. "It takes a different type of driver to stop a truck hauling 160,000 pounds. Very steady hands. No goofing." A 4-inch movement in the tractor, he says, translates to a 4-foot fishtail in the last trailer. One time, a driver lost control of the rear, and even though he kept the tractor on the road, "the trailer swung out, bit into the dirt, flipped upside down, and he dragged it like a sled."

Twenty five laps is a long time. We get to discussing trucking in general. Blake regrets that he spent so much time away from his family. "I was basically an absentee dad," he says. Perhaps this is one of the lessons of roads: If you build it, they will go. "You don't get to live your life again once you've wised up," says Blake. Unless of course, you're a pavement.

Chapter 8: Pavement has unintended consequences

The highway into Huntsville, Alabama, is reddish, almost rusty. It looks quite retro as it runs around the gleaming Saturn, Jupiter and Mercury rockets pushing their white noses up against the sky. Welcome to Tranquility Base and the Redstone Arsenal—the nation's rocket factory. The red stone that gave its name to the arsenal seems to be the aggregate in Huntsville's roads.

The move to "free the farmer from the tyranny of mud" succeeded beyond the League of American Wheelmen's wildest dreams. Roads now take up enough space to completely cover 28 percent of the state of Ohio, according to a study by the National Atmospheric and Oceanic Administration. (The remaining 72 percent of Ohio could be covered by other impermeable surfaces, such as roofs and swimming pools.)

The Global Climate and Hydrology Center at NASA's Marshall Space Center is a brown, three-story building. Inside is Dr. Dale Quattrochi, who wears a cheerful yellow shirt with flowers on it—the sort of thing you might wear to ride your safety bike around the rings of Saturn. He studies pavement, not from a dolly but from a jet: The big picture—how pavement changes our lives, the weather, the planet. Pavement (as well as roofs and other impermeables) can raise the temperature of a city like Atlanta by 2 to 8 degrees, creating what Quattrochi calls "urban heat islands."

To see pavement on his scale, Quattrochi sends very sensitive infrared cameras up in NASA jets that fly at 15,000 feet over cities—Atlanta; Baton Rouge, Louisiana; Salt Lake City; Sacramento, California. What he sees is that new black asphalt can get as hot as 135 degrees on a steamy day in Atlanta. Old asphalt, which is more reflective, tops out at 125 degrees. Concrete, with even higher reflectivity, stops at around 120 degrees. A really hot black roof, on the other hand, can reach 170 degrees. A stand of trees: 70 degrees.

Pavement creates its own climate. Radiating heat even after the sun has set, roads blast hot air upward in a vertical current like a chimney, creating unpredictable storms. The effects of these storms may be exacerbated by pavement at the end of the process as well, when the impermeable surface prevents natural runoff. And if a city has high levels of air pollution, pavement can make it worse. A study by researchers at Lawrence Berkeley National Laboratory in California found that an increase of one degree of heat increases ozone levels by 3 percent. Quattrochi is combining his databases with those of the Centers for Disease Control to research the relationship between air quality and human health, including such things as asthma attacks, and it seems as if all of the problems will get worse. By 2025, some researchers estimate as much as 80 percent of the world's population will have followed roads into cities, where they'll build residences that require ever more roads, and create ever-growing heat islands.

It may, indeed, as professor J.T. Harvey claimed, be easier to send a man to the moon than to build a perfect pavement—a heat-reflective, water-permeable, flexible, sturdy road. Which of those early 20th-century scorchers could have predicted that the roads they lobbied for would end up scorching the earth?

So before I leave Alabama I hassle Buzz to let me ride a bike over the pavement of the future. Then I hassle Brian Henry of the Auburn Bike Shop to lend me a bike, since there are no rentals in Auburn. Unbelievably, given the incoherence of my request, he helps me out and, when the truck drivers take their 7:30 a.m. break, I hit the track.

I would like to tell you that I heard my tires gripping the pavement and I could feel the viscosity of tire and pavement communing, but it would be a lie. I wish I'd actually seen the pavement grow softer in the morning sun. I wish I'd been able, like a shaman, to intuit a mysterious ailment deep inside the asphalt. Instead, I felt my retinas shriveling from the glare. I strained to ride and balance my notebook. I listened for the tread beating the asphalt like a hammer and, failing that, created my own pavement sound classification system: singing, crackling, maracas, static and "tiny bartender with tiny cocktail shaker."

Then I stopped thinking and just began riding, faster and faster and faster. The air rushed by my ears. The aggregate rocks beneath me formed psychedelic patterns. I slowed, once, out of respect for a squished armadillo, its armor and jointed tail flattened by the trucks, its short arms out as if it had been crucified. Then I pedaled on, rolling over the asphalt on my bike.

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